Advantech PCI-1751 User Manual page 12

Usi n g Ju m p e r s t o Se t Po r t s as Ou t p u t Po r t s
By shorting the lower two pins of the jumpers JPA0, JPB0, JPC0L,
JPC0H, JPA1, JPB1, JPC1L or JPC1H, a user sets the corresponding
ports to be output ports. (JPA0 means jumper for port A0, JPB0
means jumper for port B0, etc.) Shorting the lower two pins of a
port's jumper pins disables the port from being software configurable
as an input port. The initial state of each of these ports after system
power on or reset will be logic 0 (voltage low), unless jumper JP4
determines otherwise. (See Jumper JP4 below.)
Ju m p e r JP4 Re st o r e s Po r t s t o Th e i r Co n d i -
t i o n Pr i o r t o Re se t
Jumper JP4 gives the PCI-1751 a new and valuable capability. With JP4
enabled, the PCI-1751 "memorizes" all port I/O settings and output
values, and, in the event of a "hot" reset, the settings and output
values present at the port just prior to reset are restored to each port
following reset. This feature applies to both ports set by software, and
to ports configured as output ports via jumper. Depending on the
application, this capability may allow a card to be reset without
requiring a complete shutdown of processes controlled by the card
(since port values are left unchanged and are interrupted only momen-
tarily).
Complete loss of power to the chip clears chip memory. Thus, even if
JP4 is enabled, if the power to the card is disconnected, the card's
initial power-on state will be the default state (for software-set ports)
or the state of an output port with voltage low output (for jumper-set
ports).
When jumper JP4 is not enabled, power-off or reset results in ports
returning to their default state (for software-set ports) or returning to
the state of output port with voltage low output (for jumper-set ports).
8 PCI-1751 User's Manual
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